[snowman_al]

My initial thought was similar to PJL's, except I would make it an auto-transformer rather than buck transformer.

Then you say running it at 220 volts will drop 10 Watts? So the question is how much power does it use in normal operation at 220 volts? Not idle but in real operation. What percentage of that power is 10 watts?

Run it for an hour or two at 220 volts on the variac, then see how hot the heatsinks are. If they are much cooler there is a benefit in dropping the volts. If there is little or no difference in temperature, that is how it is...

Somewhere I have read if you can touch the case for five seconds the temperature is 65 degrees C or less.